There are numerous known examples that use pigments as colorants for high molecular organic compounds, including various printing inks such as gravure printing inks, sizing colors, binder colors, coating materials, various coating formulations, dry toners and wet toners for electrophotography, thermal transfer recording inks, inks for writing instruments, and the like (for example, JP-A-08-020731 and JP-A-08-027391).
No pigment colorants are, however, known to be fully equipped with properties such as high transparency and vividness required for coating formulations for the formation of color filter pixels and inkjet inks. Fine division of a pigment for use in these applications to a primary particle size level of from several tens to several hundreds nanometers in an attempt to improve its transparency and vividness, however, leads to an increase in the recoagulation power of pigment particles themselves so that the pigment is deteriorated in dispersibility and dispersion stability. Technologies making use of dispersants or the like are hence known (for example, JP-A-09-122470, JP-A-09-137075 and JP-A-2003-066224). These technologies are, however, still insufficient to obtain the properties required for the above-described applications. It is, therefore, the current circumstances that with pigment colorants prepared by the above-mentioned conventional technologies, the requirement for such high dispersibility, dispersion stability, transparency, vividness and the like cannot be fully satisfied in their entirety.